A brushless motor is generally composed of a motor and a corresponding driving circuit. As compared to a brush motor, the brushless motor has a lower running noise and a longer service life. Generally, brushless motors are classified into sensor controlled brushless motors and sensor-less brushless motors, depending on whether they are provided with sensors for detecting positions of a rotor.
For controlling with sensors, the positions of position sensors and the control method of the position sensors are important factors affecting performance of the brushless motor.